The invention is related generally to power systems for electronic devices that allow the device to be variously powered by an AC source or by non-rechargeable or rechargeable batteries. More particularly, the invention relates to battery management systems and methods adapted to automatically determine battery type and provide in-device charging.
Electronic devices capable of running on battery power or power from an AC source are widely known. Battery chemistries that are commonly used in these devices include alkaline, high-drain alkaline, high-energy lithium, nickel-metal hydride (NiMH) and nickel-cadmium (NiCd). Of these, normally only batteries having NiMH or NiCd chemistries are rechargeable. Attempts to recharge other battery types can lead to venting or leaking of electrochemical materials, and in some cases can result in dangerous explosions. The batteries used in these devices also come in different forms (i.e., sizes), including commonly available forms such AA or AAA. Instead of these conventional forms, specialized battery packs may be employed, as is often the case with rechargeable systems.
AC adapters are widely employed to connect electronic devices to an AC power source. In many existing designs, when the device is connected to an AC source, the battery is either disconnected from the system entirely or is connected in parallel with the converted AC source. The latter is employed when the AC source is used to charge the battery. In either case, it is difficult to accurately monitor the battery. In one case, the battery is completely disconnected, making it impossible to take voltage readings from or otherwise monitor the battery. When the battery is connected in parallel with the AC source, the input from the AC source interferes with monitoring the battery.
As indicated above, some electronic devices are designed to allow recharging of the battery using power supplied via the AC adapter when the device is connected to an AC source. In addition to the problems identified above, many of these designs suffer from various problems associated with the recharging feature. In many designs, an external charger is provided. External chargers can be inconvenient, as they require that the battery be removed from the device and placed in the charger.
Other designs employ rechargeable battery packs having special shapes or sizes. These packs are sometimes recharged in-device, or with an external charger. The unconventional shapes are often selected to prevent attempted recharging of standard-form, non-rechargeable batteries. While often providing adequate protection against recharging non-rechargeable batteries, these designs can be undesirable for many reasons. Specialized packs are typically more expensive to manufacture and replace than conventional batteries. They are often not as readily available as standard-form batteries. Also, use of specialized packs can complicate the design and manufacture of the devices in which they are employed.
Still other devices provide in-device or external charging in connection with standard-form batteries. These devices are intended for use with rechargeable chemistries only (i.e., NiMH or NiCd), and typically are provided with warning labels to that effect. One problem with these devices is that the warning sticker will become worn or fall off, or that the user will simply disregard or fail to notice the warning.
A further problem with many rechargeable systems is that they provide fast-charging, a process which requires applying a relatively high amount of energy to the battery in a short amount of time. This increases the risk of venting, leaking or explosion of the battery, and damage to the device, in the event that recharge is attempted upon a damaged or non-rechargeable battery.
The present invention provides a battery management system and method for electronic devices that may be powered by an AC source (using an AC adapter), or by a battery. The system includes firmware operatively coupled to the battery, where the firmware is configured to determine whether the battery is rechargeable. The system further includes a charge switch coupled to and controlled by the firmware. When the battery and AC source are coupled to the device, activating the charge switch causes a charging current to be applied from the AC source to the battery. The charge switch and firmware are configured to cause the charging current to not be applied to the battery if it is determined that the battery is not rechargeable.